Differential mechanism



F. W. SEECK v DIFFERENTIAL MCHANISM Nov. 7, 1939.

Filed Dec'. 6, 1937 3 Sheets-Sheet l l I l Patented Nov. 7, 1939 IUNITED STATES .PATENT CFFICE DIFFERENTIAL rrroinmrsrr Ferdinand W.Seeck, Lebanon, Greg. Application December 6, 1937, Serial No. 178,287

16 Claims. (Cl. 'M -313) My invention relates to diilerential mechanismsof the type used in automotive vehicles to compensate for the relativedifference in ,the rotational speeds of the rear or propelling wheels,as

n when turning a'corner, and, under such conditions, to divide equallythe driving power of the engine shaft and transmit it to the axles ofthe respective vehicle wheels.

As is well known, the diierential mechanisms IU most commonly usedinclude bevel gears, and

while various improvements in the form and construction of such bevelgear differentials have been made, these bevel gear diierentials allhave certain denite limitations, so that it has been V impossible thusfar,- regardless of the various improvements, to attain certain desiredresults.l

I have discovered that greater possibilities for a perfect differentialare oiered by eliminating bevel gears entirely and constructing adifferential in which planet pinion gears are substituted in placethereof.`

'I'he principal object of my invention is to provide a practical,eilcient differential which will cause the most power to be applied tothe wheel which has the greatest traction. I have found that this isibest obtained with spur gears of the planet type instead of bevel gears.I Another ,object of my invention is to provide a diierential which isstronger than but which nevertheless will constitute as compact a unitas the ordinary differential in which bevel gears are used. This I findpossible to accomplish with planet pinion gears which can be madecomparatively long and thereby afford greater tooth contact.

The dilerential mechanisms heretofore used in conventional automotivevehicles perform their function of equalizing and transmitting power tothe propelling wheels whenever the resistance to rotation of one wheelexceeds the resistance to rotation of the other Wheel. This equaldivision of power, while it enables one wheel Vto rotate faster than theother when the vehicle is turning a corner, is not desirable when thetractivelpower of the wheels is not equal because, under this lattercondition, the wheel which stands on a dry road surface with maximumtraction can exert no more propelling effort tha-n the wheel on slipperyground. Consequently, the vehicle in such a sit- 5o uationbecomesstalled since the eifective rotative force follows the path of leastresistance and spins the slipping wheel.

An object of my invention is to provide a difierential mechanism whichwill equally divide the 55 power transmitted tothe wheels under ordinaryf conditions and yet, under abnormal road surface conditions, when thetraction becomes unequal, will operate to divide the transmitted powerin such manner that the wheel having the most traction or road grip willreceive more rotative 5 power than the other wheel. The manner in whichI.attain the above mentioned and incidental objects by the use of piniongears in a semi-planetary arrangement, and by other improved dilerentialconstructionr will now be del0 scribed with reference to theaccompanying drawmgs.

In the drawings:

Fig. 1 is a sectional elevation on the line I-.I of Fig. 2 illustratinga simple embodiment of my l5 invention;

Fig. 2 is a transverse sectional elevation on the line 2-2 of Fig. l andcorresponding thereto;

Fig. 3 is a sectional elevation on the line 3-3 of Fig. 4 showing afurther embodiment of the 20 in Fig.4;

Fig.y 6 is a perspective view of the other axle driving element alsoshown in Fig. 4; 30

Fig. 7 is a sectional elevation corresponding to Fig. 3 but showing aslight modiiication in construction;

Fig. 8 is a fragmentary transverse sectional elevation on the line 8-8of Fig. 7; 35

Fig. 9 is a fragmentary perspective View of the pinion gear carryingmember shown in Fig. 7;

Figs. 10, 10a and 10b are explanatory diagrams illustrating theoperation of the parts of my differential shown in Figs. land 2; and 40Figs. 11a and 11b are explanatory diagrams of the operation of theembodiment of my invention illustrated in Figs. 3 and 4 and illustratingthe direction of the forces exerted in the use of this em' bodiment. 45

Referring rst to the embodiment of my invention illustrated in Figs. 1and 2, an end plate I l(Fig. 2), formed with an integral peripheralshouldered flange 2 and a central hub 3, is journaled for free rotationon the concentric axle shaft 4 and on the sleeve-like extension 5 of aspur-gear 6, the step'ped bore of the hub 3 providing the necessarybearing surfaces. The spurgear 6, which is similar in general form tothe helical gear shown in Fig. 6, is bored and splined ing such gearspermitting the axley shaft to be withdrawn for repair or replacementwithout disr'nantling the dii'ferentiai assembly and also serving toprevent rotation of the said gear l with respect to the axle shaft l. Asapparent in Fig. 2, the toothed rim of the spur-gear 8 extends beyondthe extremity of the axle shaft l and is bored to receive the concentrichub 'I of a cylindrical cup-shaped, pinion-carrying member 8, the hub 'Ibeing splined to receive the correspond ingiy splined end of an axleshaft 8 in axial alignment with the shaft I. The body of the cupshapedpinion-carrying member 8 is bored to a slightly larger diameter than theoverall diameter of the spur-gear 8 disposed therein and is rotatablymounted on the inward extension 3' of the hub I of the end plate i. Theshape of member 8 is shown in general in Fig. 5. Disposed in suitableapertures 8a (Fig. 1), provided in the comparatively thick shell of thehollow body of the member 8 are three setsof pinion gears symmetricallyarranged in semi-planetary formation about the spur-gear 5 substantiallyas shown in Fig. l, each set comprising two identical pinions i5 and iihaving stub shafts I2 and Il, respec-V tively, .iournaled in the saidshell of the member 5. The teeth of the three pinions i meshwith theteeth of the spur-gear and with the teeth of the identical pinions Ii.The teeth of the latter in turn mesh with the similar teeth of aninternal gear Il formed on the interior of a cupshaped differentialhousing I5. Thus the teeth of internal gear Il, pinions I0 and Ii, andspurgear 5 are necessarily identical in size and shape. The diameter ofthe pitch circle of the internal gear Il `is made twice that of thespur-gear 6, and, consequently, has twice as many teeth.

The hub I8 of the cup-shaped housing I5 (see Fig. 2) is provided with acentral stepped bore adapted to receive the external end of hub 1 of themember 8, and also the axle shaft 8 in such manner that the housing I5may rotate freely thereon and constitute a complete casing for theentire differential mechanism when i'lrmly secured, by means of bolts orother fasteners, to the flange 2 of the end plate I. Thus the housing I5and its attached end 'plate I, may be freely rotated on the axle shaftsl and 9, and the member 8. keyed to the axle shaft is rotatable on thespur-gear 6, keyed to the axle shaft l. The entire housing comprisingthe two portions I and I5 is rotated as a unit by means of a ring gearI1, firmly secured to the fiange 2, and a suitable pinion (not shown)mounted on the drive shaft connected with the vehicle motor.

'I'he operation of the embodiment of my invention shown in Figs. 1 and 2will now be described. For the purpose of this description the entirerange of conditions under which the differential in the vehicle operateswillbe resolved into three cases as follows: v

Case 1. when the resistance of both wheels is Case 2, when theresistance of the right wheel (mounted on the axle 9) exceeds that ofthe left wheel (mounted on the axle l); and

Case 3, when the resistance of the left wheel exceeds that of the right.

Gille 1.Rleferring to the diagrammatic drawings Fig. 10, it will be seenthat rotation in a counter-clockwise direction of the housing I5 has atendency to cause the rotation also in a counter-clockwise direction ofthe pinion Il and in the opposite direction of the pinion I5. Therotative force applied on pinion il at A equals (approximately) therotative force applied by pinion I8 on spur-gear 8 at the point C. Therotative power applied at point A on member l would ordinarily be twicethe rotative power applied at point C on spur-gear 5 due to the factthat point A is approximately twice the distance oi' point C from thecenter of the axis of rotation of housing I5, member 8 and spur-gear 8;but the power at point A is divided yand ene-half of this force acts asa tendency to rotate member 8 in a counter-clockwise direction andone-half, acting thru the medium of the pinions II and I0, is exerted atC in the form of a tendency to rotate spur-gear 8 in a counter-clockwisedirection. Since both member 8 and spur-gear 8 offer the sameresistance, these tendencies are balanced, and as a result both member 8and spur-gear 5 are driven in unison in the same direction and at thesame speed as the housing I5, the pinions II and III being held againstrotation. The entire differential under such condition operates as aunit, and as a result both wheels of the vehicle turn at the same speedand in the same direction. The result obtained in this case, therefore,is precisely the same as that obtained with the conventional bevel geardifferential.

Case 2.-In this case the resistance imposed by the right hand wheel onmember 8 exceeds the resistance imposed by the left hand wheel onspur-gear 8. Referring to the diagrammatic drawing Fig. 10a, let it beassumed that the extreme condition prevails, that is, that theresistance to rotation of the right wheel is suiiiciently greater thanthat of the left wheel so that the member 8 is heldstationary.Counter-clockwise rotation of the housing I5, as before, imparts rotarymotionin a counter-clockwise direction to the pinion II and in clockwisedirection to the pinion I0, and the latter in turn imparts rotary motionin counter-clockwise directon to the spurgear 5. .Thus the spur-gear 5rotates in the same direction as the housing I5, while the member 8remains stationary. But, because of the fact that the internal gear ofthe housing I5 has double the number of teeth of the spur-gear 5, thelatter will be rotated at exactly twice the speed of the housing I5.

Case 3.-In this case the resistance imposed on spur-gear 8 by the leftwheel is assumed to be sufficiently greater than that imposed by theright wheel on member 8 so that the spur-gear 6 remains stationary.Referring to diagrammatic drawing Fig. 10b, the action of thedifferential under this condition is as follows: Counter-clockwiserotation of the housing I5 will impart clockwise rotation to the pinionii and counter-clockwise rotation to the pinion i0. Since the spurgear 6is restrained from rotation, the rotation of pinion I0 counter-clockwiseforces member 8 to rotate counter-clockwise, that is in the samedirection as the housing I5. And since the number of teeth on theinternal gear of housing I5 is twice the number on the stationaryspur-gear 6, in this case member 8 will be rotated in the same directionas housing I5 and exactly at twice the speed;

In the description of the operation of the diier- 1 ential mechanism inthese three cases, the housing I5, constituting the driving member, hasbeen described as rotating counter-clockwise but it is to be understoodthat correspondingly similar results are obtained when the housingrotates in the opposite direction, the several members being 1s merelydriven in reverse direction to that expla-ined in Cases 1, 2 and 3. Therotation of member 8 and/or spur-gear 6 in these cases is always in thesame direction as that of the driving member or housing I5.

From the above three cases the following general observations are to bemade regarding the operation of my differential, provided, of course,that the number of teeth on the internal gear of the housing I5 isalways exactly twice the number of teeth on the spur-gear 6:-when theresistance offered by both wheels is equal, both will be driven at thesame rate of speed and in the same direction; whenl the resistanceoffered by one wheel increases the speed of that wheel decreases and thespeed of the other increases accordingly until, when the resistance ofone wheel becomes suiciently greater than that of the other, the rstmentioned wheel-will remain stationary while the other wheel will bedriven at twice the speed of the housing or driving member. The speed ofthe latter, however, can never be more than twice that of the drivingmember or housing, and it will be found in this specic construction thatthe sum of the speeds of spurgear 6 and member 8 will always equal twicethe speed of the driving member I5 regardless of the variation inresistance offered by the two Vehicle wheels.

A further case should be considered at-this point, namely, the resultobtained when the housing I5 is held stationary and one of the vehiclewheels is rotated. Referring to Fig. 10, let it be assumed that thehousing I5 is kept stationary while member 8 is rotated in acounter-clockwise direction. It is desired to ascertain what effect isproduced on spur-gear 6. Assuming that member 8 rotates incounter-clockwise direction a distance of the arc measured by the spaceof two teeth on the internal gear I4, it is obvious that the pinion IIwill be rotated in clockwise direction for a distance of two teeth.Pinion II in turn will cause pinion I to rotate an equal distance in acounter-clockwise direction, which has a tendency to cause pinion IIJ totravel in a counter-clockwise direction on spur-gear 6. But, since theangle through which member 8 has rotated is measured by the arccorresponding to two teeth on gear I4 and the same angle is measured byan arc corresponding to one tooth on spur-gear 8, (the former beingtwice the diameter of the latter and consequently having twice as manyteeth, as previously specified), rotation of member 8 in acounter-clockwise direction through an angle measured by the arccorresponding to two teeth on gear I4 would be rotation through an arcmeasured by one tooth on spur-gear 6. However, during this partialrotation of member 8 the pinion II and consequently pinion I8 arerotated to the extent of two of their peripheral teeth. In other words,pinion IU must rotate on spur-gear 6 sufficiently to cause two of itsteeth successively to mesh with the similar teeth on spur-gear 6. Butsince the travel of member 8 is sulicient to take up the distance ofonly one tooth on spur-gear 6, and pinion I0 is obliged during thatperiod to mesh successively with two teeth on spur-gear 6, the pinion`l0forces the spur-gear 6 to turn in the opposite or clockwise direction tothe extentbf one tooth. Thus when member 8 rotates counter-clockwise adistance corresponding to two teeth on gear I4, spur-gear 6 is forced torotate in the opposite direction a distance of one tooth on spur-gear 6.In other words, when member 8 moves in one direction (the housing I5being held stationary) spur-gear 6 is driven in the opposite directionat the same speed. Similarly, it would be shown that when spur-gear Brotates in one direction (the housing I5 being held stationary) member 8is driven at the same speed in the opposite direction.

Thus all the functions of an ordinary bevel gear differential areperformed by-my differential having planet pinion gears.

The modification of my invention illustrated in Figs. 3 and 4 will nowbe described. A cupshaped, cylindrical housing I8 (Fig. 4) is formedwith an integral end plate I9 and peripheral ange 20 to which is firmlysecured the conventional -ring gear I1 or other suitable means fortransmitting rotary motion to the housing I8. The end plate I9 isprovided with a hub 2l having a central stepped bore adapted to receiveand be freely rotatable on the left Wheel axle shaft 4 and on thetubular extension 22 of a helical spur-gear 23. This spur-gear is shownseparately in Fig. 6. The interior surface of the tubular extension 22is formed with integral splines which cooperate with the splined end ofthe axle shaft 4 to provide a slideable but nonrotatable mounting forthe spur-gear 23 on the said axle shaft 4. The spur-gear 23 is thuskeyed. so to speak, to the axle shaft 4 and the housing I8 is freelyrotatable thereon. An end plate 24 is removably secured to the housingI8 and has a hub 25 bored to two diameters in similar manner to the hub2I of the opposite end section I9, and is freely rotatable on the rightwheel axle shaft 9 and on the hub 26 of the cupshaped pinion carryingmember 21, which is also shown in Fig. 5. The hub 26 of member 21 issplined to slideably receive the correspondingly splined end of the saidaxle shaft 9 in alignment with the axle shaft 4. The inner end of hub 26also constitutes a bearing surface for that portion of the spur-gear 23which extends over it. Member 21 has a concentric bore of slightlylarger diameter than the overall diameter of the spur-gear 23 so thatthe spur-gear 23 may be independently disposed therein, as shown in Fig.3. The maximum diameter of member 21 is sufciently less than the minimumdiameter of the internal surface of the housing I8, to provide thenecessary clearance for independent relative rotation. The internalsurface of the housing I8 is formed with an internal helical gear 28.The diameter of the pitch circle of the internal gear 28 is twice thatof the spur-gear 23 and, since the form and pitch of the two gears areidentical, there are exactly twice as many teeth in the internal gear 28asin the spur-gear 23, the construction in this respect being similar tothat described with reference to Figs. 1 and 2.

Member 21 carries a plurality of groups (preferably three) of pinionsarranged in symmetrical, planet-like formation about the spur-gear 23and disposed in suitable apertures 29 provided in the comparativelyAthick shell of member 21 and having helical teeth. of the same form andpitch as spur-gear 23 and internal gear 28. Each group of pinionscomprises two identical pinions 30 and 3| having stub shafts 32 and 33,respectively, journaled in member 21 and relatively so located that theteeth of each pinion coact with the teeth of the spur-gear 23 and withthe teeth of a third pinion 34 interposed between the two pinions 30 and3| and in registration with the internal gear 28, as shown in Fig. 3.However, the pinion 34 of each set, unlike the pinions 30 and 3I, is ailoating pinion which has no stub shafts nor other direct connectionwith member 21, but is supported in operative position only by the teethof the pinions 30 and 3l and of the internal 5 gear 28. Thus, the pinion34, when rotated by the internal gear 28, does not itself exert turningforce on member 21 but transmits the rotative force to the pinions 30and 3l.

I have found that since each floating pinion 34 does not rotate about afixed center but is supported solely by tooth contact with the pinions30 and 3I and internal gear 28, it is preferable with this constructionto have gear teeth rounded, and with such gears in helical form, asshown, I obtain a constant rolling contact of the coacting teeth and asmoother action in my differential.

The operation of this modified form of my differential will now bedescribed, the entire range of operative action being divided as beforeinto three cases.

Case 1.-When the tractability of road Iadherence of both wheels isequal, asy when the vehicle is driven in a straight course on a hardsur- 28 face road or when starting from rest on such a road, rotation ina. counter-clockwise direction of the housing I8 thru the medium of thering gear I1 causes the internal gear 28 to exert rotative force in thesame direction on the iloati0 ing pinion 34 which in turn has a tendencyto rotate the pinions 30 and 3I in the opposite (clockwise) directionwith resultant counterclockwise ei'Iort on the spur-gear 23. However,since both vehicle wheels offer the same resistance to rotation, andthus the resistance on member 21 is equal to that on spur-gear 23, therecan be no relative movement of the pinions 30, 3i and 34,

member 21 or spur-gear 23, because the rotative forces acting inopposite directions are balanced, with the result that the pinions 30,3| and 34 remain stationary and all parts of the differential mechanismare rotated as a unit in the same manner as explained in Case 1 of theoperation of the construction illustrated in Figs. 1 and 2.

Case 2.-When the resistance offered by member 21 exceeds that ofi'eredby spur gear 23. Referring to the diagrammatic drawing Fig. ila, andassuming that the resistance oiered by member 21 is such thatmember21would ordinarily tend to remain at rest, while the housing I8rotates in a counter-clockwise direction, the tendency would be, as hasbeen shown before, for spur gear 23 to rotate in a counter-clockwisedirection at twice the speed of housing I8, and pinion 30 would rotatein a clockwise direction. However, since pinion 34 is iloating" and thushas no direct connection with member 21, this floating pinion is crowdedagainst the pinion 3U by the thrust of the teeth of the internal gear28. This thrust on the iloating" pinion 34 has two direct results.First, a rolling thrusting and coupling effect is exerted between thehousing I8 and the member 21 which carries the pinion 30, and thisrolling coupling effect results in part in greater counterclockwiserotative force being exerted on member 21. Second, designating thecontacts between the housing I8 and the iloating pinion 34 by A,

the contact between floating pinion 34 and pinion 30 by B, the contactbetween pinion 30 and spur gear 23 by C, and the center of pinion 30 byE, respectively, since the pinion 34 is floating the force applied at Ais transmitted across pinion 34 to the point B. This force has twotendencies, namely, a thrust against E in the direction BE and a secondtendency to turn the pinion 30 in a clockwise direction by the force ABexerted on the crank arm EB. However, it will be apparent from thediagrammatic illustration in Fig. 11a, that the thrust against E is thegreater of these two forces, that is to say that any slight resistanceto the clockwise rotation of pinion 30 exerted by its contact withspur-gear 23 at the point C, will prevent the turning of the pinion 30and cause a greater amount of the force AB to be expended in thedirection BE. In other words, a greater force is exerted to push themember 21 in a counter-clockwise direction. But member 21 is the memberin this case which offers the greater resistance.

Case 3.-Now let it be assumed that spur-gear 23 offers the greaterresistance and that this resistance is suilicient ordinarily to causethe spurgear 23 to tend to remain stationary while the housing I8 isrotated in a counter-clockwise direction. Referring to the diagrammaticdrawing Fig. 11b, as has been previously'explained, under suchcondition, the counter-clockwise rotation of the housing I8 would tendto cause member 21 to be rotated in the same counter-clockwisedirection, but at double the speed of the housing I8, while spur-gear 23remains stationary, and pinion 34 would be rotated in a clockwisedirection and pinion 30 in a counter-clockwise direction. But this isnot exactly what happens. As in the previous case, since the pinion 34is Boating, the force is transmitted in the direction AB across thepinion. But this force AB is in opposition to the normal tendency, inthis case, of the pinion 34 to rotate in a clockwise direction.Similarly, the rotation of pinion 34 in a clockwise direction causespinion 30 torotate in counter-clockwise direction. However, the force ABtransmitted across pinion 34 to the point B has two tendencies, namely,a thrust in the direction BC and a thrust in the direction BE. Theformer tendency exerts a force in opposition to the normal rotation ofthe pinion 30 in a counter-clockwise direction. This force BC tends toresist the counter-clockwise rotation of pinion 38 and is mainlytransmitted in the approximately straight line ABC across the pinions tothe spur-gear 23 at the point C. Thus in this case a greater force isexerted on the member offering the greater resistance,

Similarly, it might be shown that rotation of the housing I8 in aclockwise direction would result, thru the iioating" pinion 34, in agreater rotative force being exerted either on member 21 or on spur-gear23, in a clockwise direction, depending upon which member oiered thegreater resistance.

A further slight modification of the construction of my differential isillustrated in Figs. '1, 8 and 9. The helical spur-gear 23 is identicalto that shown in Figs. 4 and 6. The housing 35 is provided with aninternal helical gear 36 similar to that designated 28 in Fig. 3 andlikewise of pitch diameter twice that of the spur-gear 23. The principalfeature distinguishing this modification is the location of the planetpinions and in the manner in which they are disposed in the carryingmember, the object of this alternative construction being to stillfurther increase the proportional amount of the total rotative powertransmitted to the driving element of the wheel having the greatertractive power. Fig. 7 shows a plurality of sets (preferably three) ofpinions symmetrically arranged in planetary formation about thespur-gear 23, each set comprising three identical pinions 31, 38 and 39disposed in suitable apertures in the shell of the member 40, thegeneral form of which is similar to that of member 21 in Fig. 5. Each ofthe pinions 31 and 38 is provided with a pair of stub shafts such asshown at 4| and the pinions 39 are mounted on pins 43 journaled in holes44 (Fig, 9) so disposed in member 40 that the helical teeth of thepinions 39 register ywith the teeth of the spur-gear 23. The stub shafts4| of the pinions 31 and 38 are each journaled in bearing blocks 45which are slideably disposed in recesses or pockets 46 so located inmember 40 that the active teeth of the pinions 31 and 38 are inregistration with the teeth of the pinions 39 and with the teeth of theinternal gear 36, sufficient clearance being provided therebetween as topermit of a slight amount of movement of the pinions 31 and 38 and theirbearing blocks in a direction radial to the internal gear 36. Because ofthese slideable mountings, the pinions 31 and 38 perform a similarfunction to that of the fioating pinion 34 of the embodiment shown inFig. 3, namely, to produce a rolling thrusting and coupling effect asheretofore described with reference to Case 2 of the said previousembodiment but with a greater degree of effectiveness due to the factthat two such pinions are provided in each set. Otherwise, the action ofmy differential mechanism with this modification is similar to thataction already described.

Obviously, further modifications in my differential are possible withoutdeparting from the principles of my invention. It is not my intention tolimit my invention to the exact construction of the pinions andassociated elements as described. However, I have found it essential forthe proper working of my device as a vehicle differential to have thenumber of the identical teeth of the internal driving gear twice that ofthose on the driven spur-gear as specified.

I claim:

1. A differential mechanism of the character described including a pairof axle shafts in axial alinement, a housing, an internal gearassociated with the said housing and concentric with said axles, apinion-carrying member rotatable within said housing and said internalgear and connected to one of said axles, a spur-gear rotatable withinsaid member and connected to the other of said axles, the diameter ofsaid spur-gear being one-half the diameter of the said internal gear, aplurality of sets of pinion gears in semiplanetary formation carried bysaid member, each of said sets including a pair of spaced pinionsmeshing with said spur-gear and a fioating pinion adapted to mesh withboth of said first mentioned pinions and with said internal gear.

2. In a'diferential mechanism of the character described a pair of axleshafts in axial alinement, an internal gear concentric with said axles,a pinion-carrying member rotatable within said internal gear andconnected to one of said axles, a spur-gear rotatable within said memberand connected to the other of said axles, the diameter of said spur-gearbeing one-half the diameter of the said internal gear, a plurality ofsets of pinion gears in semi-planetary formation carried by said member,each of Said sets including a pair of spaced pinions meshing with saidinternal gear and a pinion meshing with both of said first mentionedpinions and with said spur-gear.

3. A differential mechanism of the character described including a pairof axle shafts in axial alinement, a housing, an internal gearassociated with the said housing and concentric with said axles, apinion-carrying member rotatable within said housing and said internalgear and connected to one of said axles, a spur-gear rotatable withinsaid member and connected to the other of said axles, the diameter ofsaid spur-gear being one-half the diameter of the said internal gear, aplurality of sets of pinion gears in semiplanetary formation carried bysaid member, each of said sets including a pair of spaced slidablymounted pinions meshing with said internal gear and a pinion normallymeshing with both of said first mentioned pinions and with saidspur-gear.

4. In a differential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a pinion-carrying member rotatable within said' internal gear andconnected to one of said axles, a spur-gear rotatable within said memberand connected to the other of said axles, the teeth of said internalgear and said spur-gear being similar, `but said internal gear havingapproximately twice as many teeth as said spur-gear, a pair ofV spacedpinions carried by said member and meshing with said spur-gear, and apinion carried by said member and meshing with both of said firstmentioned pinions and with said internal gear.

5. In a differential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a pinion-carrying member rotatable within said internal gear andconnected to one of said axles, a spur-gear rotatable Within said memberand connected to the other of said axles, the teeth of sai-d internalgear and said spur-gear being similar but said internal gear havingapproximately twice as many teeth as said spur-gear, a plurality of setsof pinion gears in semi-planetary formation carried by said member, eachof said sets including a pair of spaced pinions meshing with saidspur-gear and a pinion adapted to mesh with both of said first mentionedpinions and with said internal gear.

6. In a differential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a pinion-carrying member rotatable within said internal gear andconnected to one 0f said axles, a spur-gear rotatable within said memberand connected to the other of said axles, a plurality of sets of piniongears in semi-planetary formation carried by said member, each of saidsets including a pair of spaced pinions meshing with said spur-gear anda pinion adapted to mesh with both of said first mentioned pinions andwith said internal gear, said internal gear, pinions, and spur-gearcomprising helical gears of the same formation and pitch, and saidinternal gear having twice as many teeth as said spur-gear.

'1. In a differential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a pinion-carrying member rotatable within said internal gear andconnected to one of said axles, a spur-gear( rotatable within saidmember and connectedt'o the other of said axles, the diameter of saidspur-gear being one-half the diameter of said internal gear, a pair ofslidably-mounted pinion gears carried by said member, saidslidablymounted gears spaced from each other but both meshing with saidinternal gear, and a third pinion carried by said member meshing withsaid spur-gear and normally meshing with bothl of said slidably mountedgears. Y

8. In a diierential mechanism of the character described, a pair of axleshafts in axial alinement, an internal gear concentric with said axles,a pinion-carrying member rotatable within said internal gear andconnected to one of said axles, a spur-gear rotatable within said memberand connected to the other of said axles, a pair o! spaced pinionscarried by said member and meshing withesaid spur-gear, and afloatingpinion adapted to mesh with both of said rst mentioned pinionsand with said internal gear.

9. In a differential mechanism of the character described, 'a pair ofaxle'shafts` in axial alinement, an internal gear concentric with saidaxles, a niember rotatable within said internal gear Yand connected toone of: said axles, a spur-gear rotatable within said member andconnected to the other of said axles, the diameter of said spurgearbeing one-half the diameter of said internal gear, said internal gearand said spur-gear connected by a seteof gears in semi-planetaryformation carried by said member, said set comprising a pair of spacedpinion gears and a floating gear normally meshing with both of saidpinion gears.

10. In a differential mechanism of the'character described, a pair ofaxle shafts in axial alinement, and internal gear concentric with saidaxles, a member rotatable within said internal gear and connected to oneof said axles, a spure gear rotatable within said member and connectedtcthe other of said axles; the diameter of said spur-gear gbeingone-half the diameter of said internal gear, a pair of slidably-mountedpinion gears carried by said member, said slidablymounted gears spacedfromieach other but both meshing with said spur-gear, and a floatingpinion meshing` with said internal gear and normally meshing with'bothof said slidably mounted gears.

l1. In a dilerential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a member rotatable within said internal gear and connected to oneof said axles, a spur-gear rotatable within said member and connected tothe other of said axles, the diameter of said spurgear being one-halfthe diameter of said internal gear, a pair of slidably-mounted piniongears carried by said member, said' slidably-mounted gears spaced fromeach other but both meshing with said internal gear, and a floatingpinion meshing with said spur-gear and normally Ymeshing with both ofsaid slidably mounted gears.

12. In a differential mechanism of the character described, a pair-ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a member rotatable within said internal gear and 'connected toone of said axles, a spur-gear rotattablewithin said member aridconnected to the other of said axles, the teeth of said internal gearand of said Yspur-gear being' similarY but said internal gear havingtwice as many teeth as said spur-gear, a pair of spaced pinions carriedby said member and meshing with said internal gear, and a oatipg pinionadapted to mesh with both of said tlrst mentioned pinions and with saidspurgear.

i3. In a-diterential mechanism of the character described, a pai; ofaxle shafts in axial alinement, an internal gear concentric with saidaxles,

a pinion-carrying member rotatable within-said internal gear andconnected to one of said axles, a spur gear rotatable within said memberand connected to the other of said axles, the diameter of said spur gearbeing one-half the diameter-of said internal gear, a pair ofVslidably-mounted pinion gears carried by said member, saidslidably-mounted gears spaced from each other but both meshing with saidspur-gear, and a third pinion meshing with said internal gear andnormally meshing with both of said slidably mounted gears.

14. In a differential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, a member rotatable within said internal gear and connected to oneof said aides, a spur-gear rotatable within said member and connected tothe otaer of said axles, the teeth of said internalegear and1of saidspur-gear being similar but said internalegear having twice as manyteeth as said spurgear, said internal gear and said spur-gear connectedby a set of gears in semi-planetary formation carried by said member,said set comprising a pair of spaced, slidably mounted gears and a thirdpinion gear normally meshing with both of said slidably mounted gears. sY,

l5. In a diferential mechanism of the character described, a pair ofaxle shafts in axial alinement, an internal gear concentric with saidaxles, Ya member rotatable within said internal gear and connected toone of said axles, a spur-gear rotat;V

able within said member and connected to the other of said axles, theteeth of said internal gear and of said spur-gear being similar but saidinternal gear having twice as many teeth as said spur-gear, a pluralityof sets of slidably mounted pinion gears in semi-planetary formationcarried by said member, each of said sets including a slidably mountedpinion meshing with said internal gear and a second slidably mountedpinion meshing with said first mentioned pinion and with'said spur-gear.

16fIn a differential mechanism, a driving member having an internalgear, a pair of axle shafts in axial alinement and concentric with saidinternal gear, an intermediate member rotatable within-said drivingmember and connected to one of saidY axles, a spur-gear rotatable withinsaid Yintermediate member and connected to the other of said axles, aplurality of sets of pinion gears in semi-planetary formation carried bysaid intermediate member; each of said sets including a pinion-gearmeshing with said spur-gear. and a second pinion meshing with said iirstmentioned pinion and with said internal gear, the diameter of saidspur-gear being one-half the diameter of said internal gear, and thenumber of teeth on said spur-gear accordingly being one-half the numberof teeth on the internal gear, whereby rotation of said driving memberwill cause equal torque to be applied to said axle shafts.

FERDINAND W. SEECK.

